I would argue that Apple’s restrictive policies on iPhone development have actually helped it’s ecosystem to grow to be vibrant and incredibly useful. I still maintain that the iPhone is the most useful piece of electronics ever made. Apple’s controversial policies has alot of the cruft out the of App store and helped maintain a very focussed user experience on the iPhone. I don’t think those policieis will have the same positive effect on the iPad in the long run. Here’s why:
The iPhone is an on-the-go device, meaning, in general, one is using it while moving, waiting or generally in the middle of something else. Therefore, you are happy that functionality is purposely kept relatively limited because, despite the thousands of apps available, you only actually want it to do a few things and whatever it does you want it to be simple and fast.
With the iPad on the other hand, because of its larger screen, you inherently want to do more with it, spend more time o on it. You want to be able to get at more of it, find more uses for it, and perhaps even (*gasp*) customize it like you do your desktop. I think, over time, it will be less about the focused user experience (which Apple has done tremendously with the iPhone) and more about what you can do with it. I’d argue this is quite different from the iPhone and yet, for all intents and purposes, the iPad is treated as the same device as the iPhone (iOS, App store, APIs, policies, etc.). There will be tremendous market pressure from Android, Playbook and other tablet ecosystems for Apple to allow the iPad to do more. Because of this, Apple will have to work alot harder to maintain its market share in the tablet space.
Perhaps one day you’ll even be able to see a file on your iPad… fat chance of that one.